Producing iron from solid iron carbide

ABSTRACT

A method of producing iron from iron carbide is disclosed. Solid iron carbide is injected into a molten bath comprising molten iron and slag and dissolves in the molten bath. An oxygen-containing gas is injected into a gas space above the surface of the molten bath to cause combustion of at least a portion of combustible material in the gas space. In addition splashes and/or droplets of molten iron and/or slag are ejected upwardly from the molten bath into the gas space above the quiescent bath surface to form a transition zone. The transition zone is a region in which heat generated by combustion of combustible material is transferred to the splashes and/or droplets of molten iron and/or slag and thereafter is transferred to the molten bath when the splashes and/or droplets of molten iron and/or slag return to the molten bath.

FIELD OF THE INVENTION

The present invention relates to a method of producing iron from ironcarbide in a metallurgical vessel containing a bath of molten iron.

SUMMARY OF THE INVENTION

According to the present invention there is provided a method ofproducing iron from iron carbide which comprises the steps of:

(i) injecting solid iron carbide into a molten bath comprising molteniron and slag and dissolving the iron carbide in the molten bath;

(ii) injecting an oxygen-containing gas into a gas space above thesurface of the molten bath to cause combustion of at least a portion ofcombustible material in the gas space; and

(iii) causing splashes and/or droplets of molten iron and/or slag to beejected upwardly from the molten bath into the gas space above thequiescent bath surface to form a transition zone in which heat generatedby combustion of combustible material is transferred to the splashesand/or droplets of molten iron and/or slag and thereafter is transferredto the molten bath when the splashes and/or droplets of molten ironand/or slag return to the molten bath.

The term “combustible material” is understood herein to mean any solid,molten and gaseous material.

By way of example, the term covers carbon monoxide and hydrogengenerated in and thereafter released from the molten bath.

The iron carbide may be obtained from any suitable source and be in anysuitable form.

Typically, a small proportion of the “iron carbide” comprises iron oreand/or FeO. As a consequence, dissolution of iron carbide in the moltenbath in step (i) introduces oxygen into the bath which can combine withdissolved carbon to form carbon monoxide which is released from the bathinto the gas space.

In one embodiment, the method comprises injecting an oxygen-containinggas into the molten bath to provide oxygen for reaction with dissolvedcarbon in the bath to form carbon monoxide which is released from thebath into the gas space.

Step (i) of the above-described method releases carbon into the moltenbath. The carbon has the dual purpose of:

(i) maintaining the molten bath as a reducing environment so as toprevent oxidation of the iron in the bath; and

(ii) providing a source of combustible material for generating heat tomaintain the molten bath at a temperature that is sufficient to dissolveiron carbide injected into the bath.

With regard to sub-paragraph (ii) above, as noted above, there is oxygenin the molten bath—which may be introduced as part of the iron carbidefeed and/or injected as part of the oxygen-containing gas in step (ii)of the method—and the oxygen reacts with a proportion of dissolvedcarbon in the molten bath and is released as carbon monoxide into thegas space above the bath surface.

The carbon monoxide is a combustible material which reacts withoxygen-containing gas in the gas space to form carbon dioxide and, as aconsequence of this reaction, generates heat which is transferred viathe transition zone to the molten bath.

In addition, a proportion of dissolved carbon reacts with carbon dioxideaccording to the Bouduard reaction to reform carbon monoxide to generatea further supply of combustible material.

In a similar reaction, a proportion of dissolved carbon reacts withsteam to reform carbon monoxide to generate a further supply ofcombustible material.

The reaction of dissolved carbon and carbon dioxide may take place inthe transition zone, with:

(i) dissolved carbon being carried into the transition zone withsplashes and/or droplets of molten iron from the molten bath; and

(ii) carbon dioxide that is in the gas space being carried into thetransition zone with oxygen containing gas injected into the gas spaceabove the molten bath.

It is preferred that the oxygen-containing gas injected into the gasspace and/or into the molten bath be air.

It is preferred that the air be pre-heated.

It is preferred particularly that the air be pre-heated to a temperatureof at least 550° C.

It is preferred that the method further comprises injecting acarbonaceous material into the molten bath and dissolving thecarbonaceous material in the bath.

The term “carbonaceous material” is understood herein to mean anysuitable source of carbon, in solid or gaseous form.

By way of example, the carbonaceous material may be coal.

Typically, the coal includes volatiles such as hydrocarbons which aresources of combustible material.

As with the carbon derived from the dissolution of the iron carbide, thecarbonaceous material has the dual purpose of:

(i) maintaining the molten bath as a reducing environment so as toprevent oxidation of the iron in the bath; and

(ii) providing a source combustible material for generating heat tomaintain the molten bath at a temperature that is sufficient to dissolveiron carbide injected into the bath.

It is preferred that the molten bath be maintained at a temperature ofat least 1350° C.

It is preferred particularly that the molten bath be maintained at atemperature of at least 1450° C.

In one embodiment it is preferred that the transition zone be formed byinjecting a carrier gas and iron carbide and/or the solid carbonaceousmaterial and/or another solid material into the molten bath via a tuyereextending through a side of the vessel that is in contact with themolten bath and/or extending from above the molten bath so that thecarrier gas and solid material cause molten iron and slag in the moltenbath to be ejected upwardly.

It is preferred particularly that the method comprises controllinginjection of carrier gas and solid material to cause molten iron and/orslag to be projected into the space above the molten bath surface in afountain-like manner.

In another embodiment it is preferred that the transition zone be formedby bottom injection of carrier gas.

In another embodiment it is preferred that the transition zone be formedby bottom injection of a carrier gas and iron carbide and/or solidcarbonaceous material and/or other solid material into the molten bathto cause upward eruption of molten iron and slag from the molten bath.

BRIEF DESCRIPTION OF THE DRAWING

The present invention is described further by way of example withreference to the accompanying drawing which is partiallyschematic/partially sectional view of an apparatus for producing molteniron in accordance with a preferred embodiment of the method of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

The apparatus shown in the FIGURE comprises a metallurgical vessel 3having a metal shell 5 and a lining 7 of refractory material which isadapted to contain a bath 9 of molten iron and slag.

The vessel 3 comprises a bottom 11, a side wall 13, a roof 15, and a gasoutlet 17.

The apparatus further comprises a single tuyere 21 which is arranged toextend downwardly into the vessel 3 through the side wall 13 to aposition at which, in use, the open end of the tuyere 21 is a shortdistance above the quiescent level of molten iron in the molten bath 9.

The apparatus further comprises a tuyere 25 extending generallyvertically into the vessel 3 through the roof 15.

In accordance with a preferred embodiment of the method of the presentinvention, iron carbide and coal entrained in a suitable carrier gas,such as nitrogen, are injected through the side tuyere 21 into themolten bath 9 of iron and slag.

The iron carbide and coal dissolve in the molten bath 9. The molten ironin the molten bath 9 is tapped periodically or continuously from thevessel 3. In this context, it is noted that the molten iron typicallycomprises 2-5 wt % carbon.

In accordance with the preferred embodiment of the method of the presentinvention the iron carbide and coal are injected through the side tuyere21 with sufficient momentum to cause splashes and droplets of molteniron and slag to be projected upwardly from the molten bath 9 in afountain-like manner to form a transition zone 27 in the gas space 29above the molten bath surface.

Furthermore, in accordance with the preferred embodiment of the methodof the present invention, a suitable oxygen-containing gas, such as hotair or oxygen-enriched air, is injected via the top tuyere 25 into thegas space 29 toward the transition zone 27. The oxygen-containing gascombusts combustible material, such as carbon monoxide and hydrogen, inthe gas space 29, and the initial momentum of the oxygen-containing gascarries the reaction products and heat generated by combustion into thetransition zone 27.

An important purpose of the transition zone 27 is to provide anenvironment for transferring heat generated by combustion in the gasspace 29 into the molten bath 9 to maintain the molten bath 9 at atemperature of at lest 1350° C., preferably at least 1450° C. This isachieved by the transfer of heat from combustion of combustible materialin the gas space 29 to the droplets and splashes of molten iron and slagin the transition zone 27 and thereafter to the molten bath 9 when thedroplets and splashes of molten iron and slag return to the molten bath9.

The carbon obtained from the dissolution of iron carbide and coal hasthe dual purpose of maintaining the molten bath 9 as a strongly reducingenvironment to prevent oxidation of iron in the molten bath 9 andproviding a source of heat to maintain the bath 9 in a molten state by:

(i) combusting CO/H₂ to CO₂/H₂O in the gas space 29, as described above;and

(ii) reforming CO₂ to CO to generate further combustible material.

The preferred embodiment of the method of the present invention alsocomprises injecting suitable slag-forming additives into a molten bath9.

The above-described method is an effective and efficient means ofproducing iron from iron carbide.

Many modifications may be made to the preferred embodiment of the methoddescribed above in relation to the FIGURE without departing from thespirit and scope of the present invention.

In the claims which follow and in the preceding description of theinvention, the words “comprising” and “comprises” are used in the senseof the word “including”, is the features referred to in connection withthese words may be associated with other features that are not expresslydescribed.

What is claimed is:
 1. A method of producing molten iron having a carbonconcentration of at least 2 wt % from iron carbide which comprises thesteps of: (i) injecting solid iron carbide into a molten bath comprisingmolten iron and slag and dissolving the iron carbide in the molten bathand thereby maintaining the molten bath in a reducing environment andgenerating solid and/or gaseous combustible material, at least some ofwhich is released into a gas space above the surface of the molten bath;(ii) injecting an oxygen-containing gas into the gas space above thesurface of the molten bath and causing combustion of at least a portionof combustible material in the gas space; (iii) causing splashes and/ordroplets of molten iron and/or slag to be ejected upwardly from themolten bath into the gas space above the bath surface to form atransition zone in which heat generated by combustion of combustiblematerial is transferred to the splashes and/or droplets of molten ironand/or slag and thereafter is transferred to the molten bath when thesplashes and/or droplets of molten iron and/or slag return to the moltenbath; and (iv) periodically or continuously tapping molten iron having acarbon concentration of at least 2 wt %.
 2. The method defined in claim1 wherein the oxygen-containing gas injected into the gas space is air.3. The method defined in claim 2 comprises preheating the air to atemperature of at least 550° C.
 4. The method defined in claim 1comprises injecting a carbonaceous material into the molten bath anddissolving the carbonaceous material in the bath.
 5. The method definedin claim 4 wherein the carbonaceous material is coal.
 6. The methoddefined in claim 1, comprising forming the transition zone by injectinga carrier gas and iron carbide and/or a solid carbonaceous materialand/or another solid material into the molten bath via a tuyereextending through a side of a vessel that contains and is in contactwith the molten bath and/or extending from above the molten bath so thatthe carrier gas and solid material cause molten iron and/or slag in themolten bath to be ejected upwardly into the gas space above the moltenbath surface.
 7. The method defined in claim 6 comprises forming thetransition zone by controlling injection of the carrier gas and solidmaterial to cause molten iron and/or slag to be projected into the gasspace above the molten bath surface in a fountain-like manner.
 8. Themethod defined in claim 1 comprises forming the transition zone bybottom injection of carrier gas.
 9. The method defined in claim 1,comprising forming the transition zone by bottom injection of a carriergas and iron carbide and/or solid carbonaceous material and/or othersolid material into the molten bath to cause upward eruption of molteniron and/or slag from he molten bath into the gas space.
 10. The methoddefined in claim 1, further including the step of injecting anoxygen-containing gas into the molten bath to provide oxygen forreaction with dissolved carbon in the bath to form carbon monoxide whichis released from the bath into the gas space.
 11. A method of producingmolten iron having a carbon concentration of between 2-5 wt % from ironcarbide which comprises the steps of: (i) injecting solid iron carbideinto a molten bath comprising molten iron and slag and dissolving theiron carbide in the molten bath and thereby maintaining the molten bathin a reducing environment and generating solid and/or gaseouscombustible material, at least some of which is released into a gasspace above the surface of the molten bath; (ii) injecting anoxygen-containing gas into the gas space above the surface of the moltenbath and causing combustion of at least a portion of combustiblematerial in the gas space; (iii) causing splashes and/or droplets ofmolten iron and/or slag to be ejected upwardly from the molten bath intothe gas space above the bath surface to form a transition zone in whichheat generated by combustion of combustible material is transferred tothe splashes and/or droplets of molten iron and/or slag and thereafteris transferred to the molten bath when the splashes and/or droplets ofmolten iron and/or slag return to the molten bath; and (iv) periodicallyor continuously tapping molten iron having a carbon concentration ofbetween 2-5 wt %.
 12. The method defined in claim 11, wherein theoxygen-containing gas injected into the gas space is air.
 13. The methoddefined in claim 12, comprising preheating the air to a temperature ofat least 550° C.
 14. The method defined in claim 11, comprisinginjecting a carbonaceous material into the molten bath and dissolvingthe carbonaceous material in the bath.
 15. The method defined in claim14, wherein the carbonaceous material is coal.
 16. The method defined inclaim 11, comprising forming the transition zone by injecting a carriergas and iron carbide and/or a solid carbonaceous material and/or anothersolid material into the molten bath via a tuyere extending through aside of a vessel that contains and is in contact with the molten bathand/or extending from above the molten bath so that the carrier gas andsolid material cause molten iron and/or slag in the molten bath to beejected upwardly into the gas space above the molten bath surface. 17.The method defined in claim 16, comprising forming the transition zoneby controlling injection of the carrier gas and solid material to causemolten iron and/or slag to be projected into the gas space above themolten bath surface in a fountain-like manner.
 18. The method defined inclaim 11, comprising forming the transition zone by bottom injection ofcarrier gas.
 19. The method defined in claim 11, comprising forming thetransition zone by bottom injection of a carrier gas and iron carbideand/or solid carbonaceous material and/or other solid material into themolten bath to cause upward eruption of molten iron and/or slag from themolten bath into the gas space.
 20. The method defined in claim 11,further including the step of injecting an oxygen-containing gas intothe molten bath to provide oxygen for reaction with dissolved carbon inthe bath to form carbon monoxide which is released from the bath intothe gas space.